<template>
  <ul class="list">
    <li
      class="item"
      v-for="item in letters"
      :key="item"
      :ref="item"
      @click="handleLetterClick"
      @touchstart="handleTouchStart"
      @touchmove="handleTouchMove"
      @touchend="handleTouchEnd"
    >{{item}}</li>
  </ul>
</template>


<script>
export default {
  props: {
    cities: Object
  },
  data() {
    return {
      touchStatus: false,
      startY: 0,
      timer: null
    };
  },
  methods: {
    handleLetterClick(e) {
      // console.log(e.target.innerText);
      this.$emit("change", e.target.innerText); //发送
    },
    //开始滑动
    handleTouchStart() {
      this.touchStatus = true;
    },
    //计算第一个字母距离屏幕的高度
    handleTouchMove(e) {
      if (this.touchStatus) {
        //A字符距离顶部的距离
        const startY = this.$refs["A"][0].offsetTop;
        console.log(startY);
        const touchY = e.touches[0].clientY - 79;
        console.log(touchY);


        const index = Math.floor((touchY - this.startY) / 18);


        if (index >= 0 && index < this.letters.length) {
          this.$emit("change", this.letters[index]);
        }


        if (this.timer) {
          clearTimeout(this.timer);
        }
        // this.timer = setTimeout(() => {
        //   const touchY = e.touches[0].clientY - 79;
        //   const index = Math.floor((touchY - this.startY) / 18);
        //   console.log(index);
        //   if (index >= 0 && index < this.letters.length) {
        //     this.$emit("change", this.letters[index]);
        //   }
        // }, 100);
      }
    },
    //结束滑动
    handleTouchEnd() {
      this.touchStatus = false;
    }
  },


  computed: {
    //把cities对象里面的内容，转成数组，方便操作
    letters() {
      const letters = [];
      for (let i in this.cities) {
        console.log(i);
        letters.push(i);
      }
      return letters;
    }
  },
  updated() {
    this.startY = this.$refs["A"][0].offsetTop;
  }
};
</script>


<style lang="stylus" scoped>
// @import '~styles/varibles.styl';
.list {
  display: flex;
  flex-direction: column;
  justify-content: center;
  position: absolute;
  top: 1.58rem;
  right: 0;
  bottom: 0;
  width: 0.44rem;


    //  color :red
  .item {
    line-height: 0.4rem;
    text-align: center;
    // color: red;
  }
}
</style>
